The present disclosure relates to a power converter, a drive, and a power steering device.
Conventionally, a drive system that drives a motor with an inverter is known. In such a drive system, since the inverter generates heat along with driving of the motor, a structure for heat dissipation has been proposed.
For example, there is a configuration in which, in a rotary electric machine (motor) control device that controls energization of a rotary electric machine having a plurality of sets of windings, power conversion circuits of a plurality of systems are provided corresponding to the sets of winding, and the thickness of a heat sink in a corresponding portion of a specific circuit is different from that of a normal circuit.
However, conventionally, it is assumed that a plurality of inverters and switching elements in the inverters are in the same energized state. No consideration is given to an efficient heat dissipation structure in the case where the heat generation amounts of the inverters and the switching elements in the inverters are different from each other.
A power converter according to a preferred embodiment of the present disclosure converts power from a power source and supplies the converted power to a motor. The power converter includes an inverter connected to a winding of the motor and including switches to generate heat along with power control operation, and a substrate on which the switches are mounted. A first switch of the switches is mounted in a first region on the substrate, and a second switch that generates more heat than the first switch is mounted in a second region having higher heat dissipation than heat dissipation of the first region.
Further, one example embodiment of a drive according to the present disclosure includes the power converter described above and a motor to which the power converted by the power converter is supplied.
Further, one example embodiment of a power steering device according to the present disclosure includes the power converter described above, a motor to which the power converted by the power converter is supplied, and a power steering mechanism that is by the motor.
The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.
Hereinafter, example embodiments of power converters, drives, and power steering devices of the present disclosure will be described in detail with reference to the accompanying drawings. However, in order to avoid the following description from being unnecessarily redundant and to make it easier for those skilled in the art to understand, a detailed description more than necessary may be omitted. For example, a detailed description of a well-known item or a redundant description of substantially the same configuration may be omitted.
In the present specification, example embodiments of the present disclosure will be described by taking, as an example, a power converter that converts electric power from a power source and supplies it to a three-phase motor having three-phase (U-phase, V-phase, W-phase) windings (sometimes referred to as “coils”). However, a power converter that converts power from a power source and supplies it to an n-phase motor having n-phase (n is an integer of 4 or more) windings such as four-phase or five-phase is also within the scope of the present disclosure.
In the present specification, the motor drive assembly 1000 including the motor 200 as a component will be described. The motor drive assembly 1000 including the motor 200 corresponds to an example of a drive of the present disclosure. However, the motor drive assembly 1000 may be a device for driving the motor 200 in which the motor 200 is not included as a component. The motor drive assembly 1000 from which the motor 200 is omitted corresponds to an example of a power converter of the present disclosure.
The motor drive assembly 1000 converts power from power sources (403 and 404 in
The motor 200 is, for example, a three-phase AC motor. The motor 200 has U-phase, V-phase and W-phase coils. The winding method of the coil is, for example, concentrated winding or distributed winding.
The first inverter 101 is connected to one ends 210 of the coils of the motor 200 and applies a drive voltage to the one ends 210, and the second inverter 102 is connected to the other ends 220 of the coils of the motor 200 and applies a drive voltage to the other ends 220. In the present specification, “connection” between parts (components) means electrical connection, unless otherwise specified.
The control circuits 301 and 302 respectively include microcontrollers 341 and 342 and the like, as described in detail later. The control circuits 301 and 302 control the driving current of the motor 200 on the basis of input signals from the current sensors 401 and 402 and angle sensors 321 and 322. Specifically, the control circuits 301 and 302 control the driving current of the motor 200 by controlling operations of the two inverters 101 and 102. As a method of controlling the driving current by the control circuits 301 and 302, for example, a control method selected from vector control and direct torque control (DTC) is used. A specific circuit configuration of the motor drive assembly 1000 will be described with reference to
The motor drive assembly 1000 is connected to a first power source 403 and a second power source 404 that are independent of each other. The power sources 403 and 404 generate a predetermined power source voltage (for example, 12V). As each of the power sources 403 and 404, for example, a DC power source is used. However, each of the power sources 403 and 404 may be an AC-DC converter or a DC-DC converter, or may be a battery (storage battery). In
The motor drive assembly 1000 includes a first system corresponding to one end 210 side of the motor 200 and a second system corresponding to the other end 220 side of the motor 200. The first system includes the first inverter 101 and the first control circuit 301. The second system includes the second inverter 102 and the second control circuit 302. The inverter 101 and the control circuit 301 of the first system are supplied with power from the first power source 403. The inverter 102 and the control circuit 302 of the second system are supplied with power from the second power source 404. Although the first control circuit 301 for the first inverter 101 and the second control circuit 302 for the second inverter 102 are illustrated in
The first inverter 101 includes a bridge circuit having three legs. Each leg of the first inverter 101 includes a high-side switching element connected between the power source and the motor 200, and a low-side switching element connected between the motor 200 and the ground. Specifically, a U-phase leg includes a high-side switching element 113H and a low-side switching element 113L. A V-phase leg includes a high-side switching element 114H and a low-side switching element 114L. A W-phase leg includes a high-side switching element 115H and a low-side switching element 115L.
As a switching element, for example, a field effect transistor (MOSFET or the like) or an insulated gate bipolar transistor (IGBT or the like) is used. In addition, a power transistor of a material other than a silicon material may be used as a switching element. When the switching element is an IGBT, a diode (freewheel) is connected in antiparallel with the switching element.
For example, the first inverter 101 includes shunt resistors 113R, 114R, and 115R in the respective legs as the current sensor 401 (see
The number of shunt resistors may be other than three. For example, two shunt resistors 113R and 114R for the U phase and the V phase, two shunt resistors 114R and 115R for the V phase and the W phase, or two shunt resistors 113R and 115R for the U phase and the W phase may be used. The number of shunt resistors to be used and the arrangement of the shunt resistors are appropriately determined in consideration of product cost, design specifications, and the like.
The second inverter 102 includes a bridge circuit having three legs. Each leg of the second inverter 102 includes a high-side switching element connected between the power source and the motor 200, and a low-side switching element connected between the motor 200 and the ground. Specifically, a U-phase leg includes a high-side switching element 116H and a low-side switching element 116L. A V-phase leg includes a high-side switching element 117H and a low-side switching element 117L. A W-phase leg includes a high-side switching element 118H and a low-side switching element 118L. Similarly to the first inverter 101, the second inverter 102 includes, for example, shunt resistors 116R, 117R, and 118R.
The motor drive assembly 1000 includes capacitors 105 and 106. Each of the capacitors 105 and 106 is a so-called smoothing capacitor which stabilizes the power source voltage and suppresses torque ripple by absorbing the recirculation current generated by the motor 200. Each of the capacitors 105 and 106 is, for example, an electrolytic capacitor, and the capacitance and the number of capacitors to be used are appropriately determined according to design specifications and the like.
The control circuits 301 and 302 can realize closed-loop control by controlling the position (rotation angle) of a target rotor, rotation speed, current, and the like. The rotation speed is obtained by, for example, time-differentiating the rotation angle (rad), and is represented by a rotation speed (rpm) at which the rotor rotates per unit time (for example, one minute). The control circuits 301 and 302 can also control target motor torque. The control circuits 301 and 302 may include a torque sensor for torque control, but torque control is possible even if the torque sensor is omitted. In addition, a sensorless algorithm may be provided instead of the angle sensors 321 and 322. In the present example embodiment, torque control is performed by one of the two control circuits 301 and 302 (for example, the second control circuit 302). The power supply circuits 311 and 312 generate DC voltage (for example, 3 V, 5 V) necessary for the respective blocks in the control circuits 301 and 302.
The angle sensors 321 and 322 are, for example, resolvers or Hall ICs. The angle sensors 321 and 322 are also realized by a combination of an MR sensor having a magnetoresistive (MR) element and a sensor magnet. The angle sensors 321 and 322 detect the rotation angle of the rotor of the motor 200, and output rotation signals representing the detected rotation angle to the microcontrollers 341 and 342. Depending on the motor control approach (e.g., sensorless control), the angle sensors 321 and 322 may be omitted.
The input circuits 331 and 332 receive motor current values (hereinafter referred to as “actual current values”) detected by the current sensors 401 and 402. The input circuits 331 and 332 convert the levels of the actual current values into the input levels of the microcontrollers 341 and 342 as necessary, and output the actual current values to the microcontrollers 341 and 342. The input circuits 331 and 332 are analog-to-digital conversion circuits.
The microcontrollers 341 and 342 receive the rotation signals of the rotors detected by the angle sensors 321 and 322, and receive the actual current values output from the input circuits 331 and 332. Among the two microcontrollers 341 and 342, for example, the microcontroller 342 of the second control circuit 302 that performs torque control sets a target current value according to an actual current value, a rotation signal of the rotor, and the like, generates a PWM signal, and outputs the generated PWM signal to the drive circuit 352. The microcontroller 342 of the second control circuit 302 generates a PWM signal for controlling switching operation (turn-on or turn-off) of each switching element in the second inverter 102.
On the other hand, for example, the first control circuit 301 of the two microcontrollers 341 and 342 generates an on/off signal for controlling the switching operation of each switching element in the first inverter 101, and outputs it to the drive circuit 351. By the control with the on/off signal, the switching elements of the first inverter 101 maintain either the ON state or the OFF state during the time that the switching elements in the second inverter 102 perform the switching operation a plurality of times by the PWM control, and some of the plurality of switching elements in the first inverter 101 are turned on and the others are turned off. Such an operation in the switching elements of the first inverter 101 is hereinafter referred to as a solid on/off operation.
Sharing of the control in the two control circuits 301 and 302 and the two microcontrollers 341 and 342 and sharing of the operation in the two inverters 101 and 102 may be switched between the first system and the second system. However, for convenience of description, the following description will be made on the assumption that the solid on/off operation is performed on the first system side, and the PWM control is performed on the second system side.
The drive circuits 351 and 352 are typically gate drivers. The drive circuits 351 and 352 generate control signals (for example, gate control signals) for controlling switching operation of the respective switching elements in the first inverter 101 and the second inverter 102 according to the PWM signal and the on/off signal, and give the generated control signals to the respective switching elements. The microcontrollers 341 and 342 may have the functions of the drive circuits 351 and 352. In that case, the drive circuits 351 and 352 are omitted.
The ROMs 361 and 362 are, for example, writable memories (for example, PROMs), rewritable memories (for example, flash memories), or read-only memories. The ROMs 361 and 362 store a control program including a command group for causing the microcontrollers 341 and 342 to control the inverters 101 and 102 and the like. For example, the control program is temporarily expanded in a RAM (not illustrated) at the time of booting. Hereinafter, a specific example of the operation of the motor drive assembly 1000 will be described, and a specific example of the operation of the inverters 101 and 102 will be mainly described.
The control circuits 301 and 302 drive the motor 200 by performing three-phase energization control using the first inverter 101 and the second inverter 102. Specifically, the control circuits 301 and 302 perform three-phase energization control by switching control of the switching element of the first inverter 101 and the switching element of the second inverter 102.
The current waveform illustrated in
The high-side switching element 113H and the low-side switching element 113L on the first inverter 101 side are not simultaneously turned on, and when one is turned on, the other is turned off. Similarly, the high-side switching element 116H and the low-side switching element 116L on the second inverter 102 side are not simultaneously turned on.
When the current flows from one end side to the other end side of the winding of the motor 200 as indicated by an arrow in
When the current flows from the other end side to the one end side of the winding of the motor 200 as indicated by an arrow in
For example, in the case where the current waveform illustrated in
As illustrated in
As compared with the case where both switching elements connected to both ends of the winding of the motor 200 frequently perform switching operation according to the PWM control in the conventional PWM control, in the present example embodiment, the solid on/off operation is performed on one side of the winding of the motor 200. Therefore, the amount of heat generated by the motor drive assembly 1000 is smaller than that in the conventional case.
In the motor drive assembly 1000 of the present example embodiment, out of the two inverters 101 and 102 connected to both ends of the motor 200, six switching elements 116H, 117H, 118H, 116L, 117L, and 118L provided to the second inverter 102 are high-heat generating switching elements 132 indicated by hatching in the drawing that operate according to the PWM control. In addition, out of the two inverters 101 and 102, six switching elements 113H, 114H, 115H, 113L, 114L, and 115L provided to the first inverter 101 are low-heat generating switching elements 131 indicated by white blanks in the drawing that perform a solid on/off operation.
In other words, the low-heat generating switching elements 131 are provided to one of the first inverter 101 and the second inverter 102, and the high-heat generating switching elements 132 are provided to the other of them. As described above, in the motor drive assembly 1000 of the present example embodiment, heat generation is shared in units of inverters.
Furthermore, the motor drive assembly 1000 of the present example embodiment has a hardware structure with high heat dissipation efficiency in consideration that both the switching elements 132 with high heat generation and the switching elements 131 with low heat generation are included.
The reason why the amount of heat generated in the switching element is different is not only the case where the frequency of switching is different as described above, but also the case where the applied voltage is different, the case where the composition is different, the case where the resistance of the reflux diode is different, and the like. Even when the amount of heat generated in the switching element is different for any reason, a hardware structure with high heat dissipation efficiency described below can be applied.
Hereinafter, the hardware configuration of the motor drive assembly 1000 will be described.
The motor drive assembly 1000 includes a lower housing 1001, the motor 200, a bearing holder 1002, a substrate 1003, and an upper housing 1004.
The lower housing 1001 and the upper housing 1004 house and integrate the motor 200, the bearing holder 1002, and the substrate 1003 therein. Thus, the motor drive assembly 1000 is assembled as a so-called electromechanical motor. The two inverters 101 and 102 and the two control circuits 301 and 302 for controlling the respective inverters 101 and 102 are mounted on the substrate 1003.
The upper housing 1004 also serves as a main heat sink that directly or indirectly contacts both the low-heat generating switching elements 131 and the high-heat generating switching elements 132 to dissipate heat from the entire switching elements 131 and 132. The main heat sink achieves efficient heat dissipation in the entire switching elements 131 and 132.
The bearing holder 1002 is a holder of a bearing that holds the rotation shaft of the motor 200 and, in the present example embodiment, the bearing holder also serves as a sub-heat sink that contacts a part of the substrate 1003 to promote heat dissipation. As a result, the first region and the second region having higher heat dissipation than that of the first region exist in the substrate 1003. The low-heat generating switching elements 131 is mounted in the first region, and the high-heat generating switching element 132 is mounted in the second region.
In other words, the sub-heat sink directly or indirectly contacts the high-heat generating switching element 132 mounted in the second region to dissipate heat, and promotes heat dissipation in the second region more than heat dissipation in the first region. The bearing holder 1002 also serving as a sub-heat sink contacts the back surface (the lower surface in the drawing) of the substrate 1003 to indirectly contact the switching element 132 mounted on the front surface (the upper surface in the drawing) of the substrate 1003 and dissipate heat.
In the present example embodiment, both the bearing holder 1002 and the upper housing 1004 also serve as a heat sink, but more generally, it is desirable that at least one of the housing that houses the motor 200 and the holder of the bearing that holds the rotation shaft of the motor 200 also serves as a heat sink that directly or indirectly contacts the switching element to dissipate heat. When at least one of the housing and the bearing holder also serves as a heat sink, it contributes to suppression of the number of components and space saving.
The sub-heat sink is an example of a heat dissipation structure that promotes heat dissipation in the second region more than heat dissipation in the first region, and is an example of a heat dissipation structure provided outside the substrate. As such a heat dissipation structure, in addition to the sub-heat sink, a structure in which the thickness and the material of the main heat sink are different between the first region and the second region, and a structure in which the thickness and the material of grease that mediates heat conduction between the main heat sink and the switching element are different between the first region and the second region can be considered. In addition, a structure in which the thickness and the material of the substrate are different between the first region and the second region is also considered as a heat dissipation structure that promotes heat dissipation in the second region more than heat dissipation in the first region, and in that case, it is an example of a heat dissipation structure provided inside the substrate. With such a heat dissipation structure, a desirable difference in heat dissipation is formed. In particular, when the sub-heat sink is used, a desirable difference in heat dissipation is easily formed. Next, specific examples of the arrangement of the first region and the second region and the mounting areas of the switching elements 131 and 132 will be described.
In the example illustrated in
Modifications of the arrangement of the first region and the second region and the mounting areas of the switching elements 131 and 132 will be described below.
In the modification illustrated in
Furthermore, in the modification illustrated in
In the modification illustrated in
Also in the modification illustrated in
Also in the case illustrated in
Also, in the example illustrated in
Also in the example illustrated in
The example illustrated in
Therefore, the low-heat generating switching element 131 is mounted in first region R1 on the central portion side of the substrate 1003, and the high-heat generating switching element 132 is mounted in the second region R2 on the edge portion side of the substrate 1003.
In the example illustrated in
Also in the example illustrated in
In addition, the U-phase switching elements 131 and 132 are collectively mounted on the area Ru for the U phase, the V-phase switching elements 131 and 132 are collectively mounted on the area Rv for the V phase, and the W-phase switching elements 131 and 132 are collectively mounted on the area Rw for the W phase. Then, the phases are in isotropic mounting arrangement to each other.
In the example illustrated in
In any of the modifications described above, high heat dissipation efficiency is achieved by mounting each of the switching elements 131 and 132 in the heat dissipation regions R1 and R2 according to the amount of heat generation. In addition, since the heat dissipation efficiency in the circuit on the substrate 1003 corresponding to a power converter is high, miniaturization and high output of the electromechanical motor corresponding to a drive are realized.
Vehicles such as automobiles are generally equipped with a power steering device. A power steering device generates an auxiliary torque for assisting the steering torque of the steering system generated by the driver operating the steering handle. The auxiliary torque is generated by the auxiliary torque mechanism, and the burden on the driver's operation can be reduced. For example, the auxiliary torque mechanism includes a steering torque sensor, an ECU, a motor, a reduction mechanism, and the like. The steering torque sensor detects the steering torque in the steering system. The ECU generates a drive signal based on the detection signal of the steering torque sensor. The motor generates an auxiliary torque according to the steering torque based on the drive signal, and transmits the auxiliary torque to the steering system via the reduction mechanism.
The motor drive assembly 1000 of the above example embodiment is suitably used for a power steering device.
The electric power steering device 2000 includes a steering system 520 and an auxiliary torque mechanism 540.
The steering system 520 includes, for example, a steering handle 521, a steering shaft 522 (also referred to as a “steering column”), free shaft joints 523A and 523B, and a rotating shaft 524 (also referred to as a “pinion shaft” or “input shaft”).
The steering system 520 also includes, for example, a rack and pinion mechanism 525, a rack shaft 526, left and right ball joints 552A and 552B, tie rods 527A and 527B, knuckles 528A and 528B, and left and right steering wheels (for example, left and right front wheels) 529A and 529B.
The steering handle 521 is connected to the rotating shaft 524 via the steering shaft 522 and the free shaft joints 523A and 523B. The rack shaft 526 is connected to the rotating shaft 524 via the rack and pinion mechanism 525. The rack and pinion mechanism 525 has a pinion 531 provided to the rotating shaft 524 and a rack 532 provided to the rack shaft 526. The right steering wheel 529A is connected to the right end of the rack shaft 526 via the ball joint 552A, the tie rod 527A and the knuckle 528A in this order. Similar to the right side, the left steering wheel 529B is connected to the left end of the rack shaft 526 via the ball joint 552B, the tie rod 527B and the knuckle 528B in this order. Here, the right side and the left side correspond to the right side and the left side as seen from the driver sitting on the seat, respectively.
According to the steering system 520, steering torque is generated when the driver operates the steering handle 521, and is transmitted to the left and right steering wheels 529A and 529B via the rack and pinion mechanism 525. As a result, the driver can operate the left and right steering wheels 529A and 529B.
The auxiliary torque mechanism 540 includes, for example, a steering torque sensor 541, an ECU 542, a motor 543, a speed reduction mechanism 544, and a power supply device 545. The auxiliary torque mechanism 540 applies auxiliary torque to the steering system 520 from the steering handle 521 to the left and right steering wheels 529A and 529B. The auxiliary torque is sometimes referred to as “additional torque”.
As the ECU 542, for example, the control circuits 301 and 302 illustrated in
Of the elements illustrated in
The steering torque sensor 541 detects the steering torque of the steering system 520 applied by the steering handle 521. The ECU 542 generates a drive signal for driving the motor 543 based on a detection signal from the steering torque sensor 541 (hereinafter, referred to as a “torque signal”). The motor 543 generates an auxiliary torque according to the steering torque based on the drive signal. The auxiliary torque is transmitted to the rotating shaft 524 of the steering system 520 via the speed reduction mechanism 544. The speed reduction mechanism 544 is, for example, a worm gear mechanism. Auxiliary torque is further transmitted from the rotating shaft 524 to the rack and pinion mechanism 525.
The power steering device 2000 is classified into a pinion assist type, a rack assist type, a column assist type, or the like, depending on the part where the auxiliary torque is applied to the steering system 520.
Not only a torque signal but also a vehicle speed signal, for example, can be input to the ECU 542. The microcontroller of the ECU 542 can PWM-control the motor 543 based on a torque signal, a vehicle speed signal, or the like.
The ECU 542 sets a target current value at least based on the torque signal. It is preferable that the ECU 542 sets the target current value in consideration of the vehicle speed signal detected by the vehicle speed sensor and further in consideration of the rotation signal of the rotor detected by the angle sensor. The ECU 542 can control the drive signal of the motor 543, that is, the drive current so that the actual current value detected by the current sensor (see
According to the power steering device 2000, the left and right steering wheels 529A and 529B can be operated by the rack shaft 526 by utilizing the combined torque obtained by adding the auxiliary torque of the motor 543 to the steering torque of the driver. In particular, by using the motor drive assembly 1000 of the above example embodiment, it is possible to realize downsizing and an increase in the power output of the motor drive assembly 1000, and to realize space saving and stabilization of assist power in the power steering apparatus 2000.
Note that, in an example used in the above description, power is supplied to the motor in which the windings of each phase are not connected to each other by the inverter connected to both ends of the windings. However, in the power converter and the drive of the present disclosure, power may be supplied to the motor by, for example, a single inverter, or power may be supplied to, for example, a double star motor. In the case of supplying power to a double-star motor, for example, a high-heat generating switching element may supply power to one of the double stars, and a low-heat generating switching element may supply power to the other of the double stars.
Further, in the above description, a power steering device is mentioned as an example of the usage in the power converter and the drive of the present disclosure. However, the usage of the power converter and the drive of the present disclosure is not limited to those described above. They are applicable to a wide range including a pump and a compressor.
The above-described example embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present disclosure is shown not by the above-described example embodiment but by the scope of the claims, and is intended to include all changes within the meaning and scope equivalent to the scope of claims.
Features of the above-described example embodiments and the modifications thereof may be combined appropriately as long as no conflict arises.
While example embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.
Number | Date | Country | Kind |
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2019-063435 | Mar 2019 | JP | national |
This is a U.S. national stage of application No. PCT/JP2020/006207, filed on Feb. 18, 2020, and priority under 35 U.S.C. § 119(a) and 35 U.S.C. § 365(b) is claimed from Japanese Patent Application No. 2019-063435, filed on Mar. 28, 2019, the entire disclosures of which are hereby incorporated herein by reference.
Filing Document | Filing Date | Country | Kind |
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PCT/JP2020/006207 | 2/18/2020 | WO | 00 |